Miller capacitance tolerant buffer element

Abstract

A buffer includes a source follower module and a pull-up/pull-down module that is connected to the source follower module. An output signal at the output terminal of the source follower module follows an input signal at the input terminal with a predetermined delay, independent of the Miller capacitance. The pull-up/pull-down module pulls the output of source follower to supply/ground rail.

1. A buffer element for use in a clock tree and data path, the buffer element comprising:
 a source follower module having an input terminal and an output terminal, wherein an output signal at the output terminal follows an input signal at the input terminal with a predetermined delay as the gain of the source follower module is less than or close to unity; and 
 a pull-up/pull-down module connected to the source follower module, the pull-up/pull-down module having an input terminal connected to the source follower module output terminal and an output terminal connected to the source follower module output terminal, wherein the pull-up/pull-down module pulls the output of the source follower module to supply/ground rail, and wherein the predetermined delay is independent of Miller capacitance. 
 
     
     
       2. The buffer element of  claim 1 , wherein the output terminal of the source follower module is an output voltage terminal. 
     
     
       3. The buffer element of  claim 1 , wherein the source follower module comprises:
 a first Positive-Channel Metal Oxide Semiconductor (PMOS) transistor having a gate connected to the input terminal of the source follower module, a source connected to the output terminal of the source follower module and a drain connected to ground; and 
 a first Negative Metal Oxide Semiconductor (NMOS) transistor having a gate connected to the input terminal of the source follower module, a source connected to the output terminal of the source follower module and a drain connected to a supply voltage. 
 
     
     
       4. The buffer element of  claim 3 , wherein the pull-up/pull-down module comprises an inverter having an input terminal connected to the input terminal of the pull-up module, and an output terminal. 
     
     
       5. The buffer element of  claim 4 , wherein the pull-up/pull-down module further comprises:
 a second NMOS transistor having a gate connected to the output terminal of the inverter, a drain connected to the output terminal of the pull-up/pull-down module and a source connected to ground; and 
 a second PMOS transistor having a gate connected to the output terminal of the inverter, a drain connected to the output terminal of the pull-up/pull-down module and a source connected to the supply voltage. 
 
     
     
       6. A buffer element for use in a clock tree or data path, the buffer element comprising:
 a source follower module having an input terminal and an output terminal, wherein an output signal at the output terminal follows an input signal at the input terminal with a predetermined delay as gain of the source follower module is less than unity; and 
 a pull-up/pull-down module connected to the source follower module, the pull-up/pull-down module having an input terminal connected to the input terminal of the source follower module, and an output terminal connected to the output terminal of the source follower module, wherein the pull-up/pull-down module pulls the output of source follower to supply/ground rail, and wherein the delay is independent of Miller capacitance. 
 
     
     
       7. The buffer element of  claim 6 , wherein the output terminal of the source follower module is an output voltage terminal. 
     
     
       8. The element of  claim 6 , wherein the source follower module comprises:
 a first PMOS transistor having a gate connected to the input terminal of the source follower module, a source connected to the output terminal of the source follower module and a drain connected to ground; and 
 a first NMOS transistor having a gate connected to the input terminal of the source follower module, a source connected to the output terminal of the source follower module and a drain connected to a supply voltage. 
 
     
     
       9. The buffer element of  claim 8 , wherein the pull-up module comprises an inverter having an input terminal connected to the input terminal of the pull-up module, and an output terminal. 
     
     
       10. The buffer element of  claim 9 , wherein the pull-up/pull-down module further comprises:
 a second NMOS transistor having a gate connected to the output terminal of the inverter module, a drain connected to the output terminal of the pull-up/pull-down module and a source connected to ground; and 
 a second PMOS transistor having a gate connected to the output terminal of the inverter module, a drain connected to the output terminal of the pull-up/pull-down module and a source connected to the supply voltage.